JPH04275610A - Clock generating circuit - Google Patents

Abstract

PURPOSE:To prevent a logic circuit from malfunctioning by generating a clock whose oscillation frequency is lower than specified when ambient temperature rises above a prescribed range. CONSTITUTION:An oscillator 1 oscillates at the specific frequency and an oscillator 2 oscillates at a lower frequency than the oscillator 1. The outputs of both the oscillators 1 and 2 are connected to a switching circuit 3, the measurement signal of a temperature sensor 5 is compared by a decision circuit 4 with a prescribed value, and the comparison result is supplied to the switching circuit 3. The clock of the logic circuit 6 is supplied from the output of the switching circuit 3. When the ambient temperature rises above the specific range, the operation speed of the logic circuit 6 becomes slow and the circuit does not operate at the clock frequency. The deviation in the ambient temperature from the specific range is detected by the temperature sensor 5 and decision circuit 4. Consequently, the logic circuit 6 is prevented from malfunctioning.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clock generation circuit.

0002

2. Description of the Related Art Conventionally, a clock generation circuit has one or more oscillators with a fixed oscillation frequency, and the frequency is switched during testing.

0003

[Problems to be Solved by the Invention] Conventional clock generation circuits suffer from the problem of C
Since the operating speed of MOS logic circuits and the like becomes slow, normal operation may be impaired at a predetermined clock frequency.

0004

[Means for Solving the Problems] The clock generation circuit of the present invention includes a first oscillator, a second oscillator whose oscillation frequency is lower than the first oscillator, a temperature sensor that measures ambient temperature, and an output of the temperature sensor that is set to a specified value. and a switching circuit that switches the output of the oscillator based on the output signal of the determining circuit.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 1 is a circuit diagram of an embodiment of the present invention. Oscillator 1
generates a predetermined frequency F1, and the oscillator 2 generates a frequency F2 lower than F1. The outputs of these oscillators 1 and 2 are connected to a switching circuit 3, and a determination circuit 4 compares the measurement signal of the temperature sensor 5 with a specified value, and the comparison result is supplied to the switching circuit 3. The clock for logic circuit 6 is supplied from the output of switching circuit 3.

The operating clock frequency F1 of the logic circuit 6 is the highest frequency F1 that allows normal operation when the ambient temperature is within a predetermined range. When the ambient temperature rises above this predetermined range, the operating speed of the logic circuit 6 becomes slow and it no longer operates at the clock frequency F1. In this embodiment, the temperature sensor 5 and the determination circuit 4 detect such deviation of the ambient temperature from a predetermined range. When a temperature rise above a specified value is detected, the switching circuit 3 selects the output of the F2 oscillator 2 and supplies it to the logic circuit 6. That is, the clock frequency is lowered than a predetermined value to enable the logic circuit 6 to operate.

[0007]

As described above, the present invention can prevent malfunctions of logic circuits by generating a clock whose oscillation frequency is lower than a predetermined value when the ambient temperature rises beyond a predetermined range.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

[Explanation of symbols]

1 Oscillator 2 Oscillator 3 Switching circuit 4 Judgment circuit 5 Temperature sensor 6 Logic circuit

Claims (1)

[Claims] Claim 1: A first oscillator, a second oscillator with a lower oscillation frequency, and a temperature sensor that measures ambient temperature.
A clock comprising: a determination circuit that determines whether the output of the temperature sensor exceeds a specified value; and a switching circuit that switches outputs of the first and second oscillators based on an output signal of the determination circuit. generation circuit.